1. Field of the Invention
The present invention relates to a dielectric composition having excellent dielectric characteristics and electrical characteristics and a preparation method thereof.
2. Description of the Related Art
In accordance with the recent trend for high performance, slim and light devices within the electronics industry, high performance, miniaturization, and weight reductions have been demanded in electronic components. In particular, as computer central processing units (CPUs) have increased in speed and devices have been slimmed lightened, digitalized and multi-functionalized, research into technology for implementing characteristics such as miniaturization, thinning, high capacitance, low impedance within a high frequency region, and the like, in a multilayered ceramic capacitor (MLCC) has been actively conducted.
A perovskite powder, used as a material for a dielectric layer of an MLCC, has largely been prepared using a solid state reaction method, a co-precipitation method, or the like. However, since these methods produce crystalline structures in a high temperature calcination process, the high temperature calcination process and a grinding process are required, and the crystalline particle size is irregular.
The dielectric layer configuring the multilayered ceramic capacitor is required to be relatively thin in order to implement miniaturization and high capacitance in the MLCC. In the case in which the dielectric layer is thinned, when the perovskite power has a relatively large particle diameter, surface roughness of the dielectric layer is increased, and a short-circuit ratio is increased, such that an insulation defect may be generated.
Therefore, a fine-grained perovskite power has been demanded.
Meanwhile, in the case of manufacturing an MLCC using the fine-grained powder, it is necessary to perform a firing process at a high temperature to improve density of the ceramic powder or induce particle growth, in order to implement desired MLCC characteristics.
Here, as the powder contains fine grains, particle growth may be rapidly generated during a firing process.
In the case in which the particle growth is rapidly generated, it is difficult to control conditions to allow for the implementation of a uniformly fine structure in the dielectric layer, and it is difficult to secure a high degree of electrical reliability.
Further, as the powder contains relatively small particles, solidification with added components during the firing process is easily generated.
In the case in which solidification is excessive, a volume ratio of a pure ceramic powder capable of exhibiting dielectric characteristics of the final product is decreased, such that a dielectric constant may be deteriorated.
The final multilayered ceramic electronic component may have a fine structure including a core formed of pure ceramic powder and a shell formed of ceramic powder with an additive dissolved therein, such that the fine structure is referred to as a core-shell structure.
In general, the additive is coated on a surface of the ceramic powder, or the ceramic powder having the core-shell structure is prepared in order to have a uniform core-shell structure.
However, coating the additive on the surface of the ceramic powder may be defective, in that a coating layer may be flaked off during the firing process or there may be no remaining coating layer in the final fired body because of rearrangement due to diffusion.
In addition, in the case of using the ceramic powder having the core-shell structure, since a crystallographic-orientation of the core part and that of the shell part are different, a change in the dielectric constant may be high, depending on a temperature, and a combination of the additive and the ceramic powder is broken, such that the particle size may be non-uniform.